The present invention relates to an optically variable security element for securing valuable articles, a method for manufacturing such a security element and a data carrier that is equipped accordingly.
For protection, data carriers, such as value or identification documents, or other valuable articles, such as branded articles, are often provided with security elements that permit the authenticity of the data carriers to be verified, and that simultaneously serve as protection against unauthorized reproduction. Security elements having viewing-angle-dependent effects play a special role in safeguarding authenticity, as these cannot be reproduced even with the most modern copiers. Here, the security elements are furnished with optically variable elements that, from different viewing angles, convey to the viewer a different image impression and, depending on the viewing angle, display for example another color or brightness impression and/or another graphic motif.
In this context, optically variable security elements are known that display different movement or tilt effects when the security element is tilted, such as moving bars, moving pictorial depictions, pump effects or three-dimensional depictions. To implement the optically variable appearances, in the background art, different techniques are used that typically permit some of said movement effects to be realized particularly well and others less well.
For example, with moire magnification arrangements based on microfocusing elements and microimages, particularly moving periodic motifs can be depicted well. In contrast, tilt images or depictions having an excellent center position, that is, a view that at the same viewing angle always looks the same in all security elements produced, are often difficult to realize due to the required high-accuracy registration of the microfocusing elements and microimages.
Through nested depictions that become visible at different tilt angles, holograms can, in principle, display arbitrary animations, but the quality and luminosity of the depictions are strongly dependent on good lighting. This applies similarly to security elements having micromirror arrangements if the different views of an animation are to be nested, even if micromirror arrangements are normally brighter than holograms.
In optically variable security features based on printing inks having magnetically aligned reflective pigments, the produced effects are very bright, but to realize a certain movement effect, corresponding magnets are also always needed to align the pigments, which in practice severely limits the variety of effects and the resolution.
The optically variable effects mentioned are often difficult to individualize, that is, for example, to adjust to a certain currency or a certain value numeral. A widespread possibility for individualization consists in a demetalization in some regions, in which an effect layer is omitted in some regions, for instance in the form of a value numeral. However, such inverse texts are comparatively inconspicuous, increasing the risk that a counterfeiter uses, for example, an authentic security element from a banknote having a low value to counterfeit a banknote having a higher value without it attracting the attention of the untrained or cursory viewer.